The present invention relates to a radio communication system and further relates to primary and secondary stations for use in such a system and to a method of operating such a system. While the present specification describes a system with particular reference to the emerging Universal Mobile Telecommunication System (UMTS), it is to be understood that such techniques are equally applicable to use in other mobile radio systems.
There are two basic types of communication required between a Base Station (BS) and a Mobile Station (MS) in a radio communication system. The first is user traffic, for example speech or packet data. The second is control information, required to set and monitor various parameters of the transmission channel to enable the BS and MS to exchange the required user traffic.
In one embodiment of UMTS control channels are maintained in both directions between BS and MS once a connection has been established. This is only a relatively small overhead when speech data is being transmitted. However, in the case of packet data having a low duty cycle (i.e. intermittent transmission of packets using only a small proportion of the available channel capacity), the maintenance of bidirectional control channels represents a significant overhead.
An object of the present invention is to reduce the overhead imposed by maintaining control channels for a connection transferring data having a low duty cycle.
According to a first aspect of the present invention there is provided a radio communication system comprising a primary station and a plurality of secondary stations, the system having a communication channel between the primary station and a secondary station, the channel comprising an uplink and a downlink control channel for the transmission of control information, and a data channel for the transmission of data packets, characterised in that the primary and secondary stations have traffic reduction means for reducing traffic in the uplink and downlink control channels, and control means for activating the traffic reduction means.
According to a second aspect of the present invention there is provided a primary station for use in a radio communication system having a communication channel between the primary station and a secondary station, the channel comprising an uplink and a downlink control channel for the transmission of control information, and a data channel for the transmission of data packets, characterised in that traffic reduction means are provided for reducing traffic in the downlink control channel, and control means are provided for activating the traffic reduction means.
According to a third aspect of the present invention there is provided a secondary station for use in a radio communication system having a communication channel between the secondary station and a primary station, the channel comprising an uplink and a downlink control channel for the transmission of control information, and a data channel for the transmission of data packets, characterised in that traffic reduction means are provided for reducing traffic in the uplink control channel, and control means are provided for activating the traffic reduction means.
According to a fourth aspect of the present invention there is provided a method of operating a radio communication system comprising a primary station and a plurality of secondary stations, the system having a communication channel between the primary station and a secondary station, the channel comprising an uplink and a downlink control channel for the transmission of control information, and a data channel for the transmission of data packets, characterised by the primary and secondary stations being able to reduce traffic in the uplink and downlink control channels.